Lubricant



Patented Dec. 10, 1940 UNITED STATES LUBRICANT Ernest M. Marks, Lansdowne, and James W. Johnson, Philadelphia, Pa., as'signors to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania Serial No. 64,542

No Drawing. Application February 18, 1936,

4 Claims! (01. 252-47) The present invention relates to the prevention of corrosion of bearing metals during the lubrication thereof with hydrocarbon oils, and relates particularly to the prevention or inhibition of corrosion of copper-silver-cadmium and coppernickel-lead bearings during the lubrication thereof with highly refined or paraffinic oils such as Pennsylvania lubricating oils, oils produced by solvent-extraction processes, or oils from mixedbase lubricating stocks refined by heavy acid treatment.

It has been found that highly refined lubricating oils such as those produced by the modern solvent extraction processes, and parafl'inic oils of the Pennsylvania type, cause corrosion of bearing metals, and particularly the copper-silvercadmium alloys employed in the crankcase bearings of internal combustion engines, when operating temperatures of the order of 300 F. to 340 F. and higher are encountered. Temperatures of this order are frequently attained when engines are operated at high speeds over extended periods of time. Such corrosion is usually evidenced by the pitting or etching of the bearing surfaces and in severe cases, by the loss in weight of the bearings.

We have found that such corrosion may be prevented or substantially inhibited by adding to lubricating oils of the character described, a small quantity of an organic inhibiting agent, for example, less than about 1% by weight of the oil. Quantities of inhibiting agents of the order of 0.3% to 0.05%, or even less, have been found to effect the desired result. Among the agents which we have found suitable for use in accordance with our invention may be mentioned the following:

thiourea; the substituted thioureas such as phenyl thiourea, diphenyl thiourea, di-o-tolyl thiourea, and di-p-tolyl thiourea; thiodiphenylamine; furfuramide; p-hydroxy phenyl morpholine; 2 amino 4 nitrophenol; m-dinitrobenzene; and trinitrobenzene. It is preferable that the inhibiting agents to be added to the lubricating oil have boiling points sufliciently higher than the temperature to which the oil is to be subjected in order that excessive vaporization of the inhibiting agent does not occur.

In preparing our non-corrosive lubricating oils,

We have further found that inhibiting agents which are not readily soluble in lubricating oils may be more readily incorporated therein when such oils contain synthetic esters such as the alkyl or aryl phosphates, phthalates, oleates, stearates, naphthenates and the halogenated derivatives thereof. For example, a highly paraflinlc lubricating oil produced by solvent extraction, to which has been added about 1.5% by weight of tricresyl phosphate, will readily dissolve 0.2% of dlphenyl thiourea, whereas the same oil, in the absence of tricresyl phosphate, will only dissolve about 0.025% of diphenyl thiourea. Other synthetic esters which may be suitably employed are, for example, butyl and cetyl phosphate, chlorinated phenyl and cresyl phosphates, butyl phthalate, ethyl oleate, chlorinated methyl stearate, and propyl naphthenate.

To further illustrate our invention, reference is made to the following table which shows the inhibiting action of our agents when added to lubricating oil and tested at 342 F. The corrosion test was carried out in the following manner; 100 gms. of oil was placed in a glass container, the weighed test bearing (copper-silver-cadmium) was totally immersed in the oil and the container and contents were maintained at a temperature of 342 F. for 48 hours, a stream of air being bubbled through the oil at a rate of 50 c. e. per minute during the test. At the completion of the test, the bearing was washed free of oil with an alcohol-toluene-ethyl acetate mixture, dried and weighed. Loss in weight of the test bearing was attributed to corrosion. The lubricating oil employed as the base oil had a Saybolt Universal viscosity of 450 seconds at 100 F., an A. P. I. gravity of 27.7 at 60 F., a viscosity-index of 91 and a viscosity-gravity constant of 0.820.

Bearing Percent corrosion Inhibitor inhibitor (Cu-Ag-Od) by weight (mgs. change in weight/48 hours) Base oil None 28. Phenyl-thiourea 0. 02 +0. 4 o-Tolyl thiourea. 0. 03 +0. 7 Diphenyl thiourea 0. 25 0. 0

0.055 0.1 Di-o-tolyl thiourea. 0. 063 0. 0 Di-p-tolyl thiourem. 0. 20 +1. 0 Thiodiphenylamine- 0. 10 0. 0

0. 02 0. 4 Furluramide 0. 30 0. 0 p-Hydroxyphenylmorpholine 0. 30 0. 0 2 amino, 4 nitrophenol 0. 013 0. 0 m-Dinjtrobenzene 0, 30 l. 5 Sym-trinitrobenzene 0. 30 +0. 4

From the above table it will be seen that the copper-silver-cadmium test bearing, immersed in the unblended base oil at 342 F. lost about 28 milligrams weight in 48 hours, whereas the addition of small quantities of our inhibiting agents prevented corrosion or loss in weight substantially entirely. Our inhibiting agents are suitable for preventing corrosion of copper-silver-cadmium' bearings, and the aryl substituted thioureas are particularly adapted for use with the aforesaid bearings as well as for copper-nickel-lead bearings. Furthermore, the inhibitors employed in accordance with our invention, in many cases, prevent the formation of sludge which normally occurs in unblended oils during use.

For brevity, in the appended claims, the terms "Cu-Ag-Cd" and Cu-Ni-Pb will be understood to comprehend alloys of copper-silver-cadmium and copper-nickel-lead, respectively.

What we claim is:

i. A method of lubricating Cu-Ag-Cd and Cu- Ni-Pb bearings operated at elevated temperatures without substantial corrosion thereof, which comprises supplying to said bearings a hydrocarbon lubricating oil containing a small quantity of an aryl substituted thiourea. v

2. A method of lubricating Cu-Ag-Cd and Cu- Ni-Pb bearings operated at elevated temperatures without substantial corrosion thereof, which comprises supplying to said bearings a hydrocarbon lubricating oil containing a small quantityof an aryl substituted thiourea and a synthetic ester from the group consisting of alkyl and aryl phosphates, phthalates, oleates, stearates, naphthenates and the halogenated derivatives thereof.

3. A method of lubricating Cu-Ag-Cd and Cu Ni-Pb bearings operated at elevated temperatures Without substantial corrosion thereof, which comprises supplying to said bearings a hydrocarbon 011 containing a small quantity of tricresyl phosphate and about 0.05% to about 0.3% of an aryl substituted thiourea.

4. The method of preventing the corrosion of cadmium-silver and copper-lead alloy bearings by highly refined mineral lubricating oils which comprises adding to said oils an aryl substituted thiourea in small but corrosion inhibiting proportions.

ERNEST M. MARKS. JAMES W. JOHNSON. 

